In my above mentioned patent, trace amounts of radon in air streams are detected and measured by means of sensitive electronic alpha detector instrumentation. This invention is directed to the identification or fingerprinting of various trace ingredients including alpha particles and particular gas molecules carried in air flow streams in small concentrations, by interacting the air flow streams with an alpha radiation activity region of a constant known magnitude.
Various types of electronic detectors for identifying ingredients found in air are known in the prior art, as exemplified by the U.S. Patents now briefly described.
D. M. Mechlenburg in U.S. Pat. No. 4,616,501 issued Oct. 14, 1986 measures gas concentrations in air, such as Freon, by means of ultrasonic mechanical energy of at least two frequencies to be propogated into a chamber containing a known gas in unknown concentration, and measures the profile amplitude of the ultrasound energy at selected points in the chamber. This system however cannot detect and identify an unknown ingredient in air.
R. N. Compton, et al. in U.S. Pat. No. 3,803,481 issued Apr. 9, 1974 and C. F. Robinson in U.S. Pat. No. 2,820,946 issued Jan. 21, 1958 employ negative ion detectors to determine leakage of gases such as Freon. However the ion detector must be operated in a vacuum and thus does not not accomodate measurements directly in the atmosphere. Nor, does it identify unknown ingredients in air.
E. A. Jeffers in U.S. Pat. No. 4,609,875 uses a corona discharge to create an ion stream for determining concentrations of Freon in air. High voltage corona type devices are subject to drastic variation in the presence of varying humidity and operating voltages and are very difficult to make accurate and sensitive to small traces of monitored gases, and cannot distinguish unknown kinds of ingredients of air. Also high voltages necessary for operation do not permit small compact self contained instruments to be produced at reasonable prices.
Peter J. Chantry, et al. in U.S. Pat. No. 4,007,624 issued Feb. 15, 1977 provides a gas detector uses laser energy or heat energy to excite gas molecules to induce vibrations dissociating electrons from orbit. Identification of gases is achieved by tuning the laser frequency to excite particular molecules of interest. Migrating electrons are measured in a vacuum system that is not adapted to measurement of undiluted air flow directly. Thus accurate quantitative measurements are not feasible with such detectors.
Malcolm R. Uffelman in U.S. Pat. No. 4,385,516 detects and identifies chemical vapors in atmospheric air by means of radio frequency radiation tuned to the resonance absorption frequency of particular molecules sent into the atmosphere for reflection and reception in modified form to determine the absorption spectrum which can identify specific molecules present. This technique is advantageous in permitting atmospheric air to be tested, and in identifying unknown molecules present in air. It is however only applicable to mass clouds, and could not be used to determine small traces of molecules present in a small volume of air. Futhermore, it is subject to many kinds of interference with signals and electromagnetic noises in the atmosphere that could lead to erroneous and inaccurate analysis and quantitative measurements.
James E. Lovelock, et al. in U.S. Pat. No. 3,634,754 attempts to make accurate quantitative measurements of carrier gases flowing through an ionizing detector with a tritium ionizing source therein. Electron absorbing molecules are thus quantitatively measured by means of measurements of ion migration through a gas being tested. There is no way to identify a particular gas molecule other than that it is one which captures electrons. Problems occur in the ion field which of itself detracts from accurate measurements by opposing variations caused by concentrations of the gas molecules. This is compensated for by varying the frequency of electron pulses as a function of the sensed signal current and then counting the number of pulses as a quantitative measurement of gas concentration. This equipment cannot accurately detect and qualify small traces of pollutant gases in air for example because of the problems of detection of ions migrating between anode and cathode electrodes by means of anode to cathode currents.
There is not available in the prior art a system which can both identify precisely different unknown molecules present in small concentrations in an air sample and produce an accurate quantitative measurement of the different molecules.
There is not available in the prior art any accurate alpha radiation detector operable in atmospheric air and environment to give direct readings of magnitude of very low concentrations of alpha radiation without errors due to other types of radioactive radiation, contaminants in the air or environmental conditions affecting the detector operation.
It is a general objective of this invention to resolve the foregoing shortcomings of the prior art detectors and to provide instrumentation capable of identifying and/or quantitively measuring the concentration of unknown gas molecules present in air samples.
A more specific object of the invention is to provide improved electronic instrumentation for identifying molecular constituency of undiluted atmospheric air flowing through the instrument and for quantitatively measuring magnitudes of identified selectively ionizable molecules for a wide range of concentrations from very small traces to significant percentages of the sampled air.